With the arrival of aging society, an “elderly watch service” that automatically checks the safety of an elderly person who lives alone is increasingly expected. Typically, the watch service checks the condition of an elderly person by using information from a sensor installed in the home. For example, watching that uses a sensor installed in a water pot (“Watch hot line” offered by Zojirushi Corporation, http://www.mimamori.net), watching under a condition where a plurality of piezoelectric sensors are arranged in the home (“Watch link” offered by Tateyama Kagaku Group, https://www.tateyama.jp/mimamolink/outline.html), and the like are provided as services.
However, among these watching techniques, one that uses a single sensor (for example, a water pot sensor) has a problem in that the detection range over which watching is performed is narrow, and another that uses a plurality of sensors has a problem in that the cost of installing sensors is high.
Accordingly, dealt with here are watching techniques using “sound information” by which a large coverage may be achieved with fewer sensors. Some techniques of detecting unusualness and the like using sound information are known (for example, refer to Japanese Laid-open Patent Publication No. 2011-237865, Japanese Laid-open Patent Publication No. 2004-101216, Japanese Laid-open Patent Publication No. 2013-225248, Japanese Laid-open Patent Publication No. 2000-275096, Japanese Laid-open Patent Publication No. 2015-108990, Japanese Laid-open Patent Publication No. 8-329373, and the like).
In a watching system, it is determined whether a user being watched (a watched user) is in an “active state” or in an “inactive state”. Specifically, the “active state” is that, as illustrated on the left side of FIG. 1, a watched user is in their room, and is active on their feet. From the sounds resulting from a person's activity, it may be determined that the person is in an “active state”. The “inactive state” refers to a state in which, as illustrated on the right side of FIG. 1, the watched user is not in their room, or, although the watched user is in their room, they are asleep or quiet, producing no sound. From sounds produced by machines (such as a washing machine and a fan) or the like, it may be determined that the person is in an “inactive state”.
Such determination of an “active state” or an “inactive state” provides information that is useful for the accomplishment of elderly watch services, such as, for example, detection of a watched user who has fallen down, and detection of a watched user wandering at night. Note that it is desirable that, even when sounds outside the room, for example, when rain or a car produces a sound, the state in which a person is not active in the room be detected as an “inactive” state.